World powers are gathering in Switzerland in an attempt to find a diplomatic solution to Syria's three-year civil war, which has cost more than 130,000 lives drawn in regional powers to fight a proxy sectarian war. The conference nearly fell apart before it began when the UN invited Iran to participate. But what chance of success remains? Roula Khalaf, foreign editor, and Borzou Daragahi, Middle East correspondent, join Ben Hall to discuss.